This invention relates to radial bearing assemblies for supporting rotating shafts and in particular relates to sliding bearing arrangements lubricated hydrodynamically.
More specifically, the invention relates to a bearing for use in machinery where the lubricant contains both liquid and gaseous phases in the lubricant feed. In such bearings used in pumps, for example, under certain operating conditions the lubricant, which is a mixture of fluids, may, as a result of pressure or temperature change, become partially separated where some of the lubricant may change from liquid to gas either before it reaches the bearing chamber or within the chamber.
Such bearings are likely to become damaged if a proportion of the liquid lubricant is replaced with a gaseous phase at the bearing interface, since the lubricant will have insufficient viscosity to maintain a hydrodynamic film between the stationary and moving parts of the bearing.
In the case of a journal bearing the separated liquid phase will be centrifuged by the rotation of the shaft to take up any available space at a radial distance from the shaft while the gaseous phase will remain close to the shaft. Thus, the working surfaces may be enveloped in gas. This is made worse in the case of tilting pad journal bearings where there is a significant volume radially outwards from the shaft, between and outwards of the pads.
It is an object of the present invention to mitigate this problem by allowing the shaft to separate the phases by centrifugal action whilst also allowing the gaseous phase to pass readily through the bearing assembly while the liquid phase continues to provide a lubricant film between the stationary and moving parts of the bearing.